1. Field of the Invention
The present invention relates to a base station equipment for forming wireless zones in a radio communication system, and a base station control equipment which performs, in cooperation with a switching center, channel control of calls that occurred in radio stations located in the wireless zones.
2. Description of the Related Art
A code division multiple access (CDMA) system, which essentially has confidentiality and interference-resistibility, is a multiple access system in which the suppression of cochannel interference and the efficient reuse of radio frequencies are possible.
In addition, such a CDMA system is positively being applied to mobile communication systems recently due to the fact that the establishment of technologies for realizing the transmitting power control with high accuracy and high response has enabled the flexible control of radio transmission characteristics by the sector zone.
FIG. 8 shows an example of configurations for a mobile communication system to which the CDMA system is applied.
In the drawing, a mobile station 73 is located in one of wireless zones 72-1 to 72-m, each of which is individually formed by base stations 71-1 to 71-m. Each of these base stations 71-1 to 71-m is connected to a base station control station 75 via communication links 74-1 to 74-m. The base station control station 75 is connected to a mobile switching center, not shown, through a certain communication links 76-1 to 76-m.
The base station 71-1 comprises an antenna 77-1 and a radio processing part 78-1, a modem part 79-1, an assembly/disassembly part 80-1, and an E1 terminating part 81-1 cascaded between a feeding end of the antenna 77-1 and an end of the communication link 74-1.
Because the configuration of the base stations 71-2 to 71-m is identical to that of the base station 71-1, the same reference numerals, having subindexes xe2x80x9c2xe2x80x9d to xe2x80x9cmxe2x80x9d, will be assigned to corresponding composing elements hereafter and their explanation and illustration will be omitted.
The base station control station 75 comprises BTS interface parts 82-1 to 82-m individually connected to the other ends of the communication links 74-1 to 74m, voice processing parts 83-1 to 83-n individually connected to the above-mentioned mobile switching center via the communication links 76-1 to 76-n, an ATM switch 84 disposed between the BTS interface parts 82-1 to 82-m and the voice processing parts 83-1 to 83-n, and a signaling processing part 85 connected to a specific port of the ATM switch 84.
The BTS interface part 82-1 comprises an E1 terminating part 86-1 assembly/disassembly part 87-1, and an ATM interface part 88-1, which are cascaded between the other end of the communication link 74-1 and the corresponding port of the ATM switch 84.
Because the configuration of the BTS interface parts 82-2 to 82-m is identical to that of the BTS interface part 82-1, the same reference numerals, having subindexes xe2x80x9c2xe2x80x9d to xe2x80x9cmxe2x80x9d, will be assigned to corresponding composing elements hereafter and their explanations and illustrations will be omitted.
The voice processing part 83-1 comprises an ATM interface part 89-1, an assembly/disassembly part 90-1, and a speech codec 91-1, which are cascaded between the corresponding port of the ATM switch 84 and one end of the communication link 76-1.
Because the configuration of the voice processing parts 83-2 to 83-n is identical to that of the voice processing part 83-1, the same reference numerals, having subindexes xe2x80x9c2xe2x80x9d to xe2x80x9cnxe2x80x9d, will be assigned to corresponding composing elements hereafter and their explanations and illustrations will be omitted.
The signaling processing part 85 comprises an ATM interface part 92 cascaded to the corresponding port of the ATM switch 84 and a signaling terminating part 93.
In conventional examples of such configurations, the signaling processing part 85 provided on the base station control station 75 cooperates with the base stations 71-1 to 71-m connected via the switch 84, the BTS interface parts 82-1 to 82-mn and the communication links 74-1 to 74-m, and also cooperates with the above-mentioned mobile switching center so as to perform channel control based on a predetermined procedure.
In the channel controlling process, control information (signaling signal) transmitted by the signaling terminating part 93 (for simplicity, it is assumed that hereafter the control information is what is to be transmitted to the mobile station 73 via the base station 71-1) is fed to the modem part 79-1 via the ATM interface part 92, the ATM switch 84, the ATM interface part 88-1, the assembly/disassembly part 87-1, the E1 terminating part 86-1, the communication link 74-1, the E1 terminating part 81-1 and the assembly/disassembly part 80-1.
Besides, for the completed call occurred in the above-mentioned channel controlling process (for simplicity, it is assumed that the voice processing part 83-1 is assigned to the completed call by the above-mentioned mobile switching center), speech signals are fed from the mobile switching center.
In the voice processing part 83-1, the speech codec 91-1 feeds the speech signals to the BTS interface part 82-1 via the assembly/disassembly part 90-1, the ATM interface part 89-1 and the ATM switch 84.
Here, the assembly/disassembly parts 87-1 to 87-m and 90-1 to 90-n cooperate with the ATM interface parts 88-1 to 88-m and 89-1 to 89-n, under the channel control performed by the signaling processing part 85. The ATM switch 84 forms provided channels (paths) for connecting the BTS interface parts 82-1 to 82-m with the voice processing parts 83-1 to 83-n and the signaling processing part 85 (which adapts flexibly to the change of word length in the above-mentioned control information and the speech signals, and are independent from the characteristics of the control information and the speech signals have as transmission information).
In the base stations 71-1 to 71-m, the E1 terminating parts 81-1 to 81-m adapts to a transmission system applied to the communication links 74-1 to 74-m (for simplicity, it is assumed here to be a physical interface E1 provided by application of an STM system having the transmission rate of 2,048 Mbps) and accept the control information and the speech signals fed from the base station control station 75 via the communication links 74-1 to 74-m in a predetermined format.
The assembly/disassembly parts 80-1 to 80-m transform the control information and the speech signals to packets in a predetermined format receivable by the mobile station 73. The modem parts 79-1 to 79-m generate primary modulated signals by modulating the carrier signals according to the packets.
The radio processing part 78-1 to 78-m generate a transmission signals by performing a spreading process based on the direct sequence to the primary modulated signals respectively, and form the wireless zones 72-1 to 72-m by transmitting the transmission signals through the antennas 77-1 to 77-m.
In connection to this, with regard to the control information and the speech signals received from the mobile station 73 located in the wireless zone 72-1, the composing elements of the base station 71-1 and the base station control station 75 perform, unless otherwise noted, processes which are reversible in relation to the above-mentioned processes. Hence, for simplicity, explanations of these processes are omitted.
The mobile station 73 is equipped with a variable-rate speech codec based on the QCELP method, which outputs the frames shown in FIG. 9(a) as speech signals every 20 milli-seconds by encoding at a xe2x85x9 rate during, for example, the period on which the above-mentioned completed call occurred and no speech signal is fed by the caller at all.
However, during the period any speech signal is given, the above-mentioned variable-rate speech codec outputs the code words shown in FIGS. 9(b) to (d) as speech signals every 20 milli-seconds, by performing a xc2xc to full rate encoding.
When a completed call is generated in the mobile station 73, a traffic channel is assigned to the mobile station 73 based on the above-mentioned channel controlling procedure under the control of the base station control station 75.
Furthermore, the mobile station 73 as described above generates an upward transmission signal by performing a primary modulating process and a direct spreading process on code words provided by the speech codec, as mentioned above, or a frame of a predetermined word length consisting of a plurality of code words disposed with redundancy (hereafter this frame will be referred to as xe2x80x9cupward speech framexe2x80x9d), as transmission information. Therefore, the mobile station 73 generates an upward transmission signal which is transmitted to the base station 71-1.
In the base station control station 75, the above-mentioned upward speech frame is provided to the speech codec 91-1 via the base station 71-1, the communication link 74-1, the BTS interface part 82-1, the ATM switch 84, the ATM interface part 89-1 and the assembly/disassembly part 90-1. The speech codec 91-1 accumulates and expands the speech signals given as the code words included in the upward speech frame, then transforms them into a PCM signal with a bit rate of 64 kbps, and feeds the PCM signal to the mobile switching center via the communication link 76-1.
In the mobile station 73, when, during the period a completed call occurs and a conversation-state is being maintained, for example, control information for signifying transmission quality or requesting activation of handover should be transmitted to the base station 71-1, the variable-rate speech codec encodes the speech signals at the rate of which the longest codes that the control information could be included in the upward speech frame can be obtained, among the rates xe2x80x9cxe2x85x9xe2x80x9d, xe2x80x9cxc2xcxe2x80x9d, xe2x80x9cxc2xdxe2x80x9d and xe2x80x9c1xe2x80x9d corresponding to FIGS. 9(a) to (d).
Furthermore, the mobile station 73 generates a frame having the same word length as that of the predetermined ones (hereafter referred to as xe2x80x9cupward quasi-speech framexe2x80x9d), as shown in any of FIGS. 10(a) to (d), by packing the code words obtained by the encoding and the above-mentioned control information.
The mobile station 73 also generates upward transmission signals by performing the primary modulating process and the direct spreading process with the upward quasi-speech frame as the transmission information and transmits the upward transmission signals to the base station 71.
In the base station control station 75, the above-mentioned upward quasi-speech frame is provided to the assembly/disassembly part 90-1 via the base station 711, the communication link 74-1, the BTS interface part 82-1, the ATM switch 84 and the ATM interface part 89-1.
The assembly/disassembly part 90-1 discriminates whether or not the frame thus provided is an upward quasi-speech frame based on the difference in the format with the above-mentioned speech frame.
In the case that the result of the discrimination is true, the assembly/disassembly part 90-1 separates the code words and the control information included in the quasi-speech frame, and provides the former to the speech codec 91-1.
As for the latter, however, the assembly/disassembly part 90 assembles it into an ATM cell and, as shown in FIG. 8(a), provides the ATM cell to the signaling processing part 85 via the ATM interface part 89-1 and the ATM switch 84.
The control information which should be outputted by the signaling terminating part 93 and transmitted to the mobile station 73 in which a completed call has been occurred, is fed, as shown in FIG. 8(b), to the assembly/disassembly part 90-1 via the ATM interface part 92, the ATM switch 84, and the ATM interface part 89-1.
The assembly/disassembly part 90-1 varied the rate of encoding which is to be performed by the speech codec 91-1 and the code words received from the mobile switching center via the speech codec 91-1 and the corresponding control information, generates a downward quasi-speech frame to, by performing processes, which are reversible in relation to the processes performed for the upward quasi-speech frame as mentioned above.
Moreover, during the period that the signaling processing part 85 provides no control information at all, the assembly/disassembly part 90-1 performs processes, which are reversible in relation to the processes performed for the upward speech frame as mentioned above, to the speech signals fed by the mobile switching center via the speech codec 91-1.
Therefore, the base stations 71-1 to 71-m can form wireless zones 72-1 to 72-m based on the CDMA system under the channel control which the base station control station 75 performs in cooperation with the mobile switching center, and provide communication service to the mobile stations located in the wireless zones 72-1 to 72-m.
In the above-mentioned conventional example, no detailed explanation is given of the procedure of the channel control performed under control of the signaling terminating part 93 and the coordinated operations of the units adapted to the procedure.
However, as for the procedure of the channel control and the coordinated operations, explanations will be omitted in the following since they are not the features of the present invention and can be achieved by applying a variety of prior arts.
In the above-mentioned conventional example, when the voice processing parts 83-1 to 83-n are assigned to some completed call based on the channel controlling procedure performed by the signaling processing part 85, the assembly/disassembly parts 90-1 to 90-n should perform assembly of the downward quasi-speech frame or disassembly of the upward quasi-speech frame, together with the process of discriminating whether or not the information fed via the ATM interface parts 89-1 to 89-n corresponds to the above-mentioned quasi-speech frame.
Furthermore, the traffic passing through the ATM interface parts 89-1 to 89-n increases as the amount of information of the control information extracted from the upward quasi-speech frame and the control information to be built in the downward quasi-speech frame becomes larger.
Therefore, as for the ATM interface parts 89-1 to 89-n and the assembly/disassembly parts 90-1 to 90-n, load and power consumption are excessive and high-speed devices must be applied to ensure the desired response.
Besides, although such power consumption or applying high-speed devices is technically feasible, there is a high possibility of having limitations of mounting and heat design arises. Therefore it has been difficult to realize a configuration wherein a single ATM interface part and an assembly/disassembly part, having numerals xe2x80x9c89xe2x80x9d and xe2x80x9c90xe2x80x9d respectively, are shared by a plurality of speech codecs indicated by numeral xe2x80x9c91xe2x80x9d.
Furthermore, the number of the voice processing parts 83-1 to 83-n to be mounted on the base station control station 75, often becomes as large as several thousand, according to the number of the mobile stations to which communication service should be simultaneously provided via the base station control station 75.
Therefore it has been desired to realize an inexpensive, compact, and highly reliable voice processing part from the view point of reducing cost and improving work efficiency, which relates to maintenance and operation.
It is an object of the present invention to provide a base station equipment and a base station control equipment by which load distribution of processing the control information can be achieved without causing major change to hardware configuration.
It is another object of the present invention to reduce the load of the base station control equipment without degrading reliability, and to achieve efficient utilization of communication links to which a variety of transmission systems are applied, as well as relaxation of limitation related to mounting and heat design, and cost reduction and improving work efficiency related to maintenance and operation.
According to the present invention, the above-mentioned objects are achieved by a base station equipment comprising: speech signal monitoring means for extracting, specific speech signals to which control information of channel control is added among the speech signals generated by a variable rate codec in a radio station at the transmitting end; disassembly processing means for disassembling the speech signals and control information included in specific speech signals extracted by the speech signal monitoring means into individual transmission units including identification information of any one of the radio station at the transmitting end, a completed call that occurred in the radio station, or the channel assigned to the completed call under the channel control; and a means for transmitting the transmission units to the base station control station individually.
In the above-mentioned base station equipment, the control information and the speech signal included in specific speech signals received from a radio station in which a completed call occurred and the conversation-state is maintained, are disassembled into individual transmission units and transmitted to the control station.
Therefore the configuration of the base station control station is simplified compared with those in conventional examples wherein the processes for the control information and the speech signals included in the above mentioned specific speech signals are performed individually by different means.
According to the present invention, the above-mentioned objects are achieved by a base station equipment comprising: control information accumulation means for accumulating control information including identification information of any one of the radio station supposed to be the destination, the completed call occurred in the radio station, or the channel assigned to the completed call under the channel control; rate discrimination means for discriminating whether or not the encoding rate applied to generation of the speech signals, is lower than a predetermined value concerning speech signals which are received from the base station control station and include identification information of any radio station; and assembly means for generating specific speech signals by adding the control information including common identification information, among the control information accumulated by the control information accumulating means to the speech signals providing the result of the discrimination when the result of the discrimination is true; a means for transmitting the generated specific speech signals to the wireless zone.
In the above-mentioned base station equipment, the control information fed by the base station control station based on the channel controlling procedure is accumulated until the encoding rate applied in generating the speech signals fed by the base station control station becomes below a predetermined threshold value and is also transmitted to the radio station located in the wireless zone, as specific speech signals together with the speech signals.
Therefore, as long as the time length for accumulating the control information is shorter than a degree tolerable based on the channel controlling procedure, the channel control will be surely performed by the base station control station without degrading the speech quality.
According to the present invention, the above-mentioned objects are achieved by a base station equipment comprising: monitoring means for monitoring the period during which the control information including the same identification information as the identification information included in individual speech signals which are false according to the result of the discrimination performed by the rate discrimination means is being accumulated in the control information accumulation means, and for specifying the time when the length of the period exceeds a predetermined upper limit; and signaling priority means for transmitting, at the specified time, all or a portion of the control information which has been accumulated in the control information accumulation means and includes the identification information corresponding to the specified time, to the wireless zones.
In the above-mentioned base station equipment, the control information fed by the base station control station, is transmitted to the wireless zones without being accumulated in the control information accumulation means during a period exceeding the above-mentioned upper limit.
Therefore, as long as the upper limit is set to a value conforming to the channel controlling procedure, the channel control is performed with stability and precisely.
The above-mentioned objects are also achieved by the assembly means discarding the speech signals to be built in specific speech signals when specified a time point by the monitoring means.
According to the above-mentioned configuration, because the required load for transmission of the speech signals fed by the switching center is reduced, the channel control is performed with higher priority as long as the degradation of the speech quality due to the discarding the above-mentioned speech signals is within a tolerable range.
Furthermore, the above-mentioned objects are achieved by delivering the control information and the speech signals as packets adapted to the AAL protocol in segments except for the transmission segments leading to both the radio station and the base station control station.
According to the above-mentioned configuration, the standardization of processes with regard to delivery or generation among the composing elements becomes possible because the control information and the speech signals are fed as the above-mentioned packets in a standard form.
The above-mentioned objects are also achieved by forming, between the transmission segments leading to both the radio station and the base station control station, a path of the ATM layer which is an lower layer of the ATM adaptation layer, and interfacing between the ATM adaptation layer and the ATM layer.
Since assembly/disassembly is performed for the ATM cells which adapt flexibly to the change of the word length of the speech signals due to the difference in the characteristics of the control information and the speech signals and the change of the encoding rate applied to the encoding by the variable rate codec, according to the above-mentioned configuration, the packets including the control information and the speech signals are delivered transparently to the base station control equipment.
Furthermore, the above-mentioned objects are achieved by a base station control equipment comprising: channel control means for outputting or accepting, based on a predetermined procedure, control information including the identification information of any one from the radio station wherein a call occurs, the call, or the channel assigned to the call under the channel control; and exchange means for delivering the control information received by the base station equipment and the control information outputted from the channel control means, and delivering the speech signals received by the radio station and the switching center respectively.
According to the above-mentioned base station control equipment, the control information and the speech signals are transmitted to and received by each other by the exchange means simply identifying both and performing the exchange process, because the control information and the speech signals are delivered as individual transmission information or transmission units.
The above-mentioned objects are achieved by internally delivering packets adapted to the AAL protocol including the control information and the speech signals as ATM cells in the above-mentioned base station control equipment.
In the above-mentioned configuration, standardization of processes with regard to delivery or generation among the composing elements becomes possible because the control information and the speech signals are fed as the above-mentioned packets in a standard form.
Further objects and characteristics of the present invention will be clearly described in detail based on the accompanying drawings.